The invention is based on a device which has a yarn feeding wheel which is freely journalled on a fixed shaft in the device, and a feeding tape synchronously driven by the knitting machine, which tape is adapted to run over a part of the periphery of said yarn feeding wheel with a desired speed. A yarn control element associated with the yarn feeding wheel is also arranged to bring the yarn into engagement with the yarn feeding wheel and the yarn feeding tape, co-acting therewith for the positive feeding of the yarn to the knitting place with said desired speed and also to guide the yarn out of this engagement into a position outside the feeding tape on the yarn feeding wheel to interrupt the positive feeding thereof.
In the case of knitting pieces of goods with ready-made-up lengths, and also in other connections, there is a requirement for being able to positively feed a yarn in one and the same knitting system with at least two different speeds during the various parts of the knitting cycle for such goods. For example, an instance can be mentioned where one knits a "pullover", where the short, lower-most section in the form of a "waist rib" should be knitted with a first positive yarn speed for generating a first portion in the goods with a first stitch size and character. Immediately thereafter, the long breast and belly section ("body section") is to be knitted with a second, positive yarn speed for generating a second portion in the goods with a second stitch size and character. This case is described in detail in the British Patent Specification No. 1.246.625 (Hosiery and Allied Trade Research Association, Nottingham), which also shows a yarn feeding device consisting of so-called "nip rollers" which enables the desired positive feeding of a yarn with two different speeds in one and the same knitting system during various parts of the knitting cycle.
GB-A-2 109 825 already discloses a device for the positive feeding of yarn to a knitting machine. The prior art device comprises two feeding wheels of different diameter which are caused to rotate at different rotational speeds. A number of turns of the yarn to be fed to the knitting machine are wound around the second wheel and a cone and further around the first wheel where the yarn is engaged by the feeding tape. Depending on the yarn tension, the yarn comes into and out of engagement with the feeding tape. Hence, the tension of the yarn can be controlled as desired. However, this prior art apparatus is not adapted for carrying out a positive feeding of the yarn at two different, clearly defined, speeds.
The object of the present invention is to accomplish a yarn feeding device adapted for a selective positive feeding of the yarn at different speeds having a less complicated structure than that of the prior art devices.
In accordance with the present invention, this object is achieved by a device.
A further object of the present invention is to ensure a permanently correct positioning of the feeding tapes on the two yarn feeding wheels, namely that the feeding tape on the respective yarn feeding wheel should always run over the wheel at its edge remote from the crossing between the two wheels. According to one embodiment of the invention, this object is accomplished by the rotation axes of the two yarn feeding wheels forming a small, acute angle, with each axis being inclined at a smaller angle from a line perpendicular, to the normal planes of movement for the two feeding tapes. This geometrical relationship is preferably accomplished by the journalling position for the further yarn feeding wheel on the fixed shaft consisting of a hub portion, the centre axis of which forms a small acute, "positive" angle to the centre line of the fixed shaft. The first yarn feeding wheel is journalled on a hub portion concentrically arranged with the centre line of the fixed shaft. Moreover, the whole yarn feeding device is arranged to be mounted on a support ring extending horizontally above the knitting machine and parallel to the feeding tapes in a conventional manner such that the centre line of the fixed shaft on which the two yarn feeding wheels are journalled, forms a small, acute, "negative" angle absolute relative to a line perpendicular to the normal planes of movement for the two feeding tapes. The "negative" angle has a smaller absolute valve than said "positive" angle.
Another object of the present invention is to facilitate the alteration of the speed of the yarn. Therefore, according to the invention, the device has, in one embodiment, an annular guiding flange fixed to the rim of the first yarn feeding wheel facing the further yarn feeding wheel and extending axially out over a small piece of the further yarn feeding wheel, which flange is adapted to enable the smooth sliding of the yarn over it from its position on the first yarn feeding wheel into a position on the further yarn feeding wheel, and vice versa.